Tunable elastic Parity-Time symmetric structure based on the shunted piezoelectric materials

We theoretically and numerically report on tunable elastic Parity-Time (PT) symmetric structure based on shunted piezoelectric units. We show that the elastic loss and gain can be archived in piezoelectric materials when they are shunted by external circuits containing positive and negative resistances. We present and discuss, as an example, the strongly dependent relationship between the exceptional points of a three-layered system and the impedance of their external shunted circuit. The achieved results evidence the PT symmetric structures based on this proposed concept can actively be tuned without any change of their geometric configurations.